1. Field of the Invention
The present invention generally relates to an image forming device. More specifically, the present invention relates to an image forming device connected to a data processing device, and equipped with a printer unit, a copying unit which makes copies of the documents printed in the printer unit, and a document transport device for transporting printed documents from the printer unit to the copying unit.
2. Description of the Related Art Printers which print out character and image data sent from data processing devices such as personal computers are widely known. One problem with these types of printers has been that a significant amount of time is needed to print a large number of copies, especially when compared with the time that it takes a copying machine to do the same job.
An image forming device which attempts to solve this problem is disclosed in Japanese Unexamined Patent Application No. 5-107987 (1995). This image forming device is a combination of a copying unit and a printer unit, and is connected to a data processing device. The image data output from the data processing device is printed out by the printer unit, and the printed documents are then transported to an document mounting unit on the copying unit. The documents on the document mounting unit are then sequentially transported to a document reading unit, and then read and copied as instructed. Because the documents printed in the printer unit are used as the originals in the copying unit, a large number of copies can be made at a relatively high speed.
In this image forming device, the direction in which the paper is transported in the printer unit is the same as the direction in which documents are transported from the document mounting unit of the copying unit to the document reading unit. The printed documents are discharged from the printer unit and then transported to the document mounting unit in the copying unit.
Generally speaking, the size of printers which use A4-sized paper can be reduced if the A4-sized sheets are transported through the printer in the longitudinal direction, i.e., along the length of the A4 sheet. This is because the image forming unit (such as the photosensitive drum) need only be as long as the width of the A4 sheet. In addition, there are large numbers of copying machines capable of forming images on paper up to A3 size, thus the length of the image forming unit in the copying machine need only be as long as the with of an A3 sheet (which is the same as the length of an A4 sheet). When an A4 sheet is used in this type of copying machine, it can be transported through the copying machine along its width and thus increase the copying efficiency of the copying machine.
However, in the above-described image forming device which combines a printer unit with a copying unit, A4 size documents are both transported through the printer unit and discharged to the document mounting unit of the copying unit in the lengthwise direction. As a result, the efficiency of the image forming process is lowered because these documents are transported through the copying unit in the lengthwise direction, even though the image forming unit in the copying unit is capable of processing A4 size documents along their width. In addition, because the printer unit discharges documents to the original mounting unit of the copying unit in the lengthwise direction, the overall length of the image forming device is large. This makes it difficult to produce a compact image forming device.
Accordingly, it has been proposed to transport a sheet of paper through the printer unit in a first direction (for example, along the length of an A4 sheet), and then transport it in a second direction (for example, along the width of an A4 sheet) and align the documents on the document mounting unit in the copying unit. The leading and trailing edges of the documents (with respect to the second direction) on the document mounting unit can be readily aligned, however it is difficult to align the right and left edges of the documents. If the documents are fed through the copying unit in this condition, there is a risk that a paper jam may occur, or that the images formed may be positionally shifted.
In addition, because the first direction and the second direction are different, separate drive sources are required. For example, it is conceivable that two motors are arranged such that their drive directions are perpendicular to each other. This has the effect of increasing the overall size and cost of the image forming device, as well as its power consumption.